Radio detector system



Matthv 5, 1929. R, w, AMF|ELD 1,704,497

RADIO DETECTOR SYSTEM Filed July v1924 Patented Mar. 5, i929.

t unirti) arras: eers-sii* :eerice ideale? :RUSSELL W. caminan, or BERKELEY, ciiLiFoRnii-a, essierimnl vfio fr. .CUNNING- HAM, or san rR-Aiicisco, oiimiieniiia. y

. RADIO DETECTOR. sizs'inivi.

Appiication ined Juiy 3,

This invention 'relates to a'systein for detecting signals transmitted by radio waves by the aid of one oi' more electronic tubes, and more particularly to such a system in which at least some of the electronic tubes are used to regenerate the radio frequency energy'received, whereby lthe'amplitude of the signal is j. and thereby make interfering reradiationpossible. Such reradiation is very undesirable,

reo

causing as it does, annoying interference in nearby receivers.

Y It is therefore oneof theobjects of my i invention vto make it .possibleto secure regen,-V eration without oscillations, and withoutdisturbing reradiation by .the aidy ofstable ad- ,justments My invention possesses other advantageous y features, some of which, with the foregoing, will be set forth at length in the following description, where I shall .outline in full that form of the invention which I have selected for illustration in the drawings, accompanyy ing and forming part of the present application. Although Iliave shown in the drawings but one embodiment of'my invention, Ido

gnotdesire .to be limited thereto, since vthe in- 'veiition as expressed in the claims may beein-v l,bodied mother forms also.l

Referring to the drawings :I

Figure lis a wir-ing diagram of one form of my invention, used in connection with a single f tube receiver; and

Fig. 2 is a modification, in which two tubes Y are used.

In Fig. l, I show a conventional type of cir-A v cuit, ,such as antenna l, condenser 2, loading yc0113, aiidvground 4for absorbing electromagnetic radiations.

The energy received in .this circuit isy caused .to affect an electronic tube 5, which yis shown as of the usual ther-V mionic type, and hasa heated `filament or elec- .tron `emitting elect'rode, a .grid or control electrode?, and a plate or'anode 8,. lThe laA ment ,6 isheated by current supplied freni a seuree, vsuch .battery 9, and the degree et 192i. senti ivo. 723,988.

heat is controlledv by a variableresistance 10 in series with filament 6 and source 9. kIn practicing my invention, it is possible ,to arrange tube 5 either as a radio frequency ainplilier or as a detector. In the present instance I show it` as a detector. The lament 6 and grid 7 are subjected to the varying dier- Y ences in potentialinduced in a coil ll cou-pled to coil 3. These potential differences occurin accordance with the signaling energy received by the absorbing-circuit, and conform tothe Vmodulations carried by 'the radio frequency 4filament 6. In the present instance, the outputl circuit of the tube 5 includes a variable inductance, suchas a variometer 13, za source ,of

potential, such as a battery le., to maintain the potential of plate'S positive Witherespect to the filament 6, and thus .tocausea flow of electrons between these two electrodes, the volume :of which-'is controlled by lthevariation ,in potential of the gridv 7 and a telephone 300i' other form of. translating device.

As thus far-described, the circuit is entirely fanalagous tothe usual single tube 'detector system. Itlias been also `found that by ,properly tuningtlie plate circuit, as by adjustment of thevariometer '13,',itisfpossible'to' pass',

some of Jche `amplified :energy back to the iiiput circuit, and `to cause ,a reamplication of.

`this portion. Thiselfectlhas been explained v on the ground that the capacitive couplingfbetween the grid7 and plate 8 in the evacuatedtube 5 permits such a transfer to take place,

especially when the .plate or output circuit *is accurately adjusted for this effect. Itis thus evident that `iii such vregenerative schemes, whichproduceahigher vdegree of amplification, the capacitive coupling be tween the electrodes is a useful and `necessary factor.l The `difficulty comes in that .tlieVad-k .justnient for efficient regenerationis critical,l

and such regeneration is very aptto become highly unstable-and :to cause ,thetube .circuits to sustain independent oscillations. Such oscillations y.interfere materially. withl thev ,quality .ofthe reception, as :well rt, ,the

signals .tenerne ea'tent5 lble,in/ust.ebjeetieifiar vide a neutralizing coil 15, inductively coupled to coil 11 and connected to one'terminal thereof, and which forms one element of a circuit providing for an adjustable amount of energy interchange between the input and output circuits.V To make this interchange of the proper direction, coils 11 and 15 are Wound as if they were a. single continuous helix. The bottom terminal of the coil 15 lis connected to a point in the output'circuit in this case, through an adjustable condenser Y 16.y The point in the youtput circuitchosen for this connection is ad] acent the plate electrode 8. The amount of energy interchange beclosed circuit 11, 15, 18 to theincoining radio since such an arrangement is now well-known,

tween' the input and output circuits may be so adjusted by the aid of condenser 16 that the tube may be maintained at a regenerative stage, yet without any tendency to oscillate. This effect may be increased, and adjustments of condenser 16 rendered still less critical, by providing an additional capacitive coupling 17 between the plate 8 and' grid 7, whichv assists the inherent coupling that exists between them. ThisV coupling 1 7may be adjust-able also. Furthermore, in order to vsecure the maximum effect of the 'incoming signals, itis advisable to bridge coils 11, with a variable condenser 18, which tunes the frequency. l v

yThe operation of the system and its adjustment are relatively simple. If condenser 17 is used, it may be set at an intermediate position. Condenser 16 may be placedjto provide minimum capacity, and circuit 1115 18 may be tuned to the frequency of reception. Then variometer 13 is carefully adjustedpto secure regeneration, or even oscillationl To prevent reradiation, condenser 16 is varied until oscillations just cease. If

' such anadjustment'isfound'tooy critical, thel capacity of condenser 17 may be increased,Y

f5 andthe process repeated. Once the proper This tube has its input circuit connected sub-v stantially as in Fig. 1, to be sensitive to en- 'u setting of these two Acondensers is obtained, there will be little occasion for i'eadjustment,

even for a variation of material amount of the frequency of the radiant energy received. In Fig. 2, I illustrate areceiving system in which there is one stage of radio 'frequencyl amplification, secured by the aid of a tube 34, having filament 35, grid 86 and plate 37.

orgy "received in' the Vabsorbing circuit 1"-2--34-4@ A grid biasing battery 12 y is however included in the inputv circuit to pre' vent distortion, as is well understood; furthermore, no grid leak is provided. The out' Vput circuit includes the variometer 39 or otherV variable impedance, as well as a plate battery 3S. The prevention of oscillation or 'instability' is secured asin the former instance, by the aid of coil 15 and condensers 16 and 17, and the mode of operation isidentical.'

In this instance however, the adjustments are performed by listening in the phones 30, which are in the output circ-uit of the 'detector tube 19, the input circuit of which is connected age variations existing across the variable i nductance-BQ are impressed across the input Yelectrodes of tube 19, comprising the grid orv control electrode 24, andthe filamentor elecir` tronl emitting electrode 25. The temperature of this filament is controlled by the variable resistance 26, in yseries with the heating current battery' 27. u As is usual, a highre-n sistancegrid leak 28 may also be providesbetween these two electrodes, for improving the operation of the tube 19`as a detector.

The output circuit fortube 19 includes the y plate 29, the translating device. 30, at least a Y .portion of battery 38, and filament`25. lIn

case one or more stages of audio frequency amplification is desired, the translating de n vice 30 may be arranged to transmit the detected .impulses to these amplifiers. But 1 it is consideredunnecessary to show them. Instead, the translating ldevice 30 is shown as. a pair of phones that are used fory ldirectly producing the sound waves. p A small fixed kcondenser 31 is shown, shunting the phones ing oscillations andv consequent reradiation.- f

In other words, the adjustment of condensers u 16 and 17 in the amplifier stage'serves also to stabilize the detector stage, when th at Stage is'conductively coupled as indicated' to the amplifier tube. It is thereforequite feasible to tunethe plate or output circuit of tube 19j andtake advantage of this effect. For thisV Vpurpose I include a variableinductance 32 in the form of aV variometer, in the output circuit. By careful adjustment 'of this variometer, the desired regenerative effects" may be readily obtained, andduevto the stabilization in the amplifier stage, the detector circuit is also sta-bleagainst oscillations. Although I am not prepared at this timelto setforth in detail ythereason for this behavior, neverthe-y less I haververi'ified it by proper experiment.

ing an electron emitting electrode, a control electrode, and an anode, means forming an input circuit for said tube, connected between the electron emitting electrode and the control electrode, means forming an output'circuit between the anode and the electron emitting electrode, said means including a` tuning device whereby regeneration may be secured, and means for preventing the tube from producing oscillations, comprising a neutralizing circuit connected between the electron emitting electrode and the anode, including an inductance coil couplingV the two circuits, and a variable capacitance, sb adjusted as to produce an energy interchange between the two circuits of such character that regeneration is secured but local oscillations are neutralized. Y i

2. In a relay system for currents of radio frequency, an electron relay tube having select-ably tunable input and output circuits, a reactive element in addition to the inherent relay capacitance for effecting positive feed back of energyv from the output to the input circuit, and separate reactive means for effecting reverse feed back of energyfrom the out put to the input circuit whereby the relay system prevented from oscillating but will operate regeneratively, the reactances of said element and said reverse feed back means being so arranged and proportioned that the system will not oscillate but will remain in regenerating condition for a'. substantial,`

variation in the frequency of received'energy.

3. In a relay system for currents of radio frequency, an electron relay 'having grid, plate and cathode elements, selectively tunable input andvoutput circuits, means for effecting positive feed back of energy between Vsaid circuits comprising an external condenser connectedacross the grid and plate of said relay, and means for effecting reverse feed back of energy between said circuits com'- prising an inductance coupled to one of said circuits, and connected to the other oneyof said circuits thru a series condenser, said con- In testimony whereof, I have hereunto set` my hand'. n

' RUSSELL w. CAMFIELD. 

